r. Trethewey in his article 12 Basics
has raised a valid point. Why design
a system based on the lowest temperature the system may operate in when it has been
shown that oversizing can lead to substantial inefficiencies. We have found that
by operating at lower system temperatures real savings of 20 to 40
percent may be realized.
Whoa!!! How can that be??
he Department of Energy (DOE) says that the "Efficiency of our fossil fuel burning appliances may be around 85% and some gas appliances
are even higher.
How can you say that you can pick up 20 to 40
percent in fuel
savings when there is only 15% difference in the efficiency to 100%.. Good question. The problem with the
AFUE's are basically combustion efficiencies only. They don't take into consideration many factors that actually reflect the amount of fuel
being used. For example one tested system can have no insulation on it for rating while the
next system can have 3" of insulation around it. The AFUE's will be the same.
hey also don't take into consideration the type of radiation, piping system, or piping insulation that the Appliance is
connected to and also they address inefficiencies due to combustion cycling for due
to oversized equipment.
ur experience tells us that 20 TO 40%
savings is realizeable and that is what we are hoping to show you how to get with MoreThanHeat.com.
this number is realistic. We have had customers testify that these type of savings are available and
common sense tells us for various reasons that we can easily realize these savings with a little effort and that is the purpose to provide the
methodology that will allow you to cover all the variables and not just allow someone to walk in to your home and ask "what size boiler or furnace do you have??",
and then tell you lets go one size bigger in case you add on at some point. This is not what you need to know.
Start with a Detailed Heat Loss or Heat Gain
hen a heating professional comes to your home for a boiler replacement of when designing a new heating
system, he must first determine the heat loss of your home. There are two ways that contractors try to determine
heat loss; in a replacement situation some people try to measure the existing radiators or heating baseboards.
measuring the radiators makes the fatal assumption that the original heating contractor put in the exact right
amount of heating equipment.
Run don't Walk
void the guy who wants to replace your furnace with one of the same size or larger.
You should demand an detailed heat loss / heat gain analysis of your house which if completed on a computer takes 45minutes to an hour.
This is a Room by room analysis and is a more complete and scientific calculation that considers the
size of your home, the type of insulation in the walls, ceilings, and floors, the type and size of your
windows and doors. T
he last part of the equation is the temperature you want to maintain inside and the coldest
temperature you could expect to have outside.
Once all this data is factored in, a total heat loss is calculated in British thermal units per hour (Btuh)Room by Room.
As an example, let's assume that a 3,800 square foot house has A heat loss of 150,000 Btuh. That means that on the coldest night of the year, with a temperature outside of either zero or minus ten degrees, you will need a boiler that will produce 150,000 btuh at 180 degree boiler water to make up for the heat that leaks out of your home.
Simple enough right? Not necessarily. Consider what happens on all the other nights that are not
the coldest night. The average outdoor temperature throughout the entire heating season is 48 degrees F.
When your turn up your thermostat on one of these average days, that 150,000 btuh boiler kicks on and starts
pumping 180 degree water around. Two minutes later, just as you feel that first wave of heat rolling toward
you, the boiler shuts off. Because the boiler is sized for the worst case day (and then some) it is way too
big for the building at 48 degrees outside. It heats up much faster than the baseboard of radiators can
distribute the heat to the house. This causes "short cycling" which wastes fuel and leads to unnecessary wear
and tear on the heating plant. Rooms can overheat and radiators and baseboards can make strange ticking or
moaning noises. It is not the best situation.
As you can see from the chart below, the vast majority of our heating hours have temperatures well above freezing.
T he design conditions occur less that .3 percent of the heating season (approx 25 hours out
of 7,000). This chart is based on actual weather data over the last 65 years and reminds us that the vast
majority of our heating hours are at temperatures well above what your heating appliance was sized for.
Now, everyone wants a boiler that can heat up the house fast. Right? Not really. If fuel were free and people didn't mind large temperature swings every time the thermostat came on, it would be OK. However, fuel is more and more expensive and people are always more comfortable with an even temperature. The problem is that your boiler is actually too big for your house 99.7% of the time. The warmer it is outdoors, the more oversized your boiler becomes. It's like a car with engine that is just too big, an oversized boiler wastes fuel dollars. If you are interested in saving a sizable portion of your heating budget every year and be more comfortable, there is a solution to this problem.